#include<iostream>

using namespace std;


int main()
{
	long long a = 0, b = 0, n = 0;
	cin >> a >> b >> n;
	long long count = 1, sum = 0;
	
	for (count = 1; sum < n; count++)
	{
		if (count % 7 <= 5 && count % 7 >= 1)
		{
			sum += a;
		}
		else
		{
			sum += b;
		}
	}
	count--;
	cout << count << endl;

	return 0;
}